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This paper proposed a high-performance magnetic-coupled nonlinear electromagnetic generator (MNL-EMG). A high-permeability iron core is incorporated to the coil. The strong coupling between the iron core and the vibrating magnets lead to significantly improved output power and a broadened operating bandwidth. The magnetic force of the iron core to the permanent magnets and the magnetic flux density inside the iron core are simulated, and the dimension parameters of the MNL-EMG are optimized. Under acceleration of 1.5 g, the MNL-EMG can maintain high output performance in a wide frequency range of 17~30 Hz, which is 4.3 times wider than that of linear electromagnetic generator (EMG) without an iron core. The maximum output power of MNL-EMG reaches 174 mW under the optimal load of 35 Ω, which is higher than those of most vibration generators with frequency less than 30 Hz. The maximum 360 parallel-connected LEDs were successfully lit by the prototype. Moreover, the prototype has an excellent charging performance such that a 1.2 V, 900 mAh Ni-MH battery was charged from 0.95 V to 0.98 V in 240 s. Both the simulation and experiments verify that the proposed bistable EMG device based on magnetic coupling has advantages of wide operating bandwidth and high output power, which could be sufficient to power micro electronic devices.

Summary This article proposed a high-performance triboelectric-electromagnetic hybrid wind energy harvester (WEH). By adopting the revolution and rotation movements of tapered rollers, which serve as both the rotor of the electromagnetic generator (EMG) part and freestanding layers of the triboelectric nanogenerator (TENG) part, the WEH can work as a sustainable power source and a self-powered wind speed sensor. When the wind speed is 12 m/s, super-high open-circuit voltage peaks of 47.4 and 683 V can be achieved by the EMG and TENG, respectively, corresponding to the high-power outputs of 62 and 1.8 mW. It was demonstrated that the WEH can easily light up over 600 red light-emitting diodes and even a 5-W globe light. A self-powered wireless temperature and humidity sensing network was also systematically demonstrated. In summary, the proposed WEH exhibits bright future toward IoT applications, such as in border detection, smart buildings, and so on., Graphical abstract, Highlights • A triboelectric-electromagnetic hybrid generator based on tapered rollers is proposed • The high-performance WEH has been systematically optimized and tested • A self-powered anemometer system has been successfully established • The WEH shows bright prospect in future IoT applications, Electromagnetics ; Energy Resources ; Energy Systems ; Device

Carbon-based CsPbI3 perovskite solar cells (CsPbI3 C-PSCs) without hole-transporting materials have been attracting much attention because of their high stability. However, the electron transport l...

Sensors based on triboelectric nanogenerators have been widely used for energy harvesting and sensing applications, however, the applications of multidimensional information perception and interactive control are insufficient. In this paper, we present an ultra-stretchable triboelectric strip sensor (TSS) using triboelectric mechanism for controlling the objects in three-dimensional space. This facile and low-cost TSS is mainly composed of a parallel structure including three symmetric sensor strips fixed on the base and a mobile stage connected with them. Based on the coupling effect of triboelectrification and electrostatic induction, the length changes of each strip with the same finger contacting point generate different signal output ratios from two terminal electrodes, functioning as the interactive interface for multi-dimensional sensing and controlling. Hence, the parallel sensor strips structure can realize the sensing and controlling in three degrees of freedom of linear motion and two degrees of freedom of rotational motion, and resultant sensing ranges are X, Y, Z, α and β (20 mm, 20 mm, 30 mm, 36°, and 36°). In terms of manipulation, this is simpler than the conventional controller with rigid structure and includes additional space dimensions. Furthermore, demonstration of the TSS as human-nanomachine terminal to control the nanomanipulator in scanning electron microscope (SEM) is successfully realized with the accuracy of 10 nm. The proposed TSS shows great potential for the applications in automated control, robotics control, and Internet of Things (IoT).

Summary: The CsPbI3 inorganic perovskite is a potential candidate for fabricating long-term operational photovoltaic devices owing to its intrinsic superb thermal stability. However, the carbon-based CsPbI3 perovskite solar cells (C-PSCs) without hole transport material (HTM) are currently disadvantaged by their relatively low power conversion efficiency resulting from the poor grain quality and mismatched energy band levels of the as-made CsPbI3 films. Herein we demonstrate that by doping Na into the CsPbI3 lattice, the grain quality is significantly improved with low defect density, and also, the energy band levels are better matched to the contact electrodes, affording a higher built-in potential. Consequently, the Voc of the C-PSCs is drastically increased from 0.77 to 0.92 V, and the efficiency from 8.6% to 10.7%, a record value for the CsPbI3 PSCs without HTM. Moreover, the non-encapsulated device showed virtually no performance degradation after 70 days of storage in air atmosphere. : Energy Sustainability; Materials Characterization; Energy Materials Subject Areas: Energy Sustainability, Materials Characterization, Energy Materials

Directly dispersing graphene into an electrolyte still remains a crucial difficulty in electrodepositing a graphene enhanced composite coating onto electrical contact materials. Herein, graphene was synthesized via electrochemical exfoliation in an N,N-dimethylformamide (DMF)/H2O solution containing (NH4)2SO4. The electrochemically exfoliated graphene nanosheets (GNs) were directly dispersed by sonication. In comparison with graphene synthesized from aqueous solution, the GNs electrochemically exfoliated in the DMF/H2O–(NH4)2SO4 solution exhibit a lower degree of oxidation. Cu/graphene composite coatings were subsequently electrodeposited onto Cu foils by adding Cu2+ into the as-fabricated graphene solution. The surface nanostructure of the Cu/graphene composite coatings was transformed from loose pine needles to a uniform and compact structure with an increase in the concentration of Cu2+, which indicated that the controllable synthesis of Cu/graphene composite coatings with different performances could be achieved in graphene dispersions after adding Cu2+. In order to synthesize graphene via electrochemical exfoliation and directly electrodeposit a Cu/graphene composite coating without adding CuSO4 or any other additive, an attempt was made to directly electrodeposit a Cu/graphene composite coating in CuSO4/DMF/H2O solution after electrochemical exfoliation.

More versatile and effective strategies are needed to prepare high-quality perovskites and their precursors for promoting the efficiency of perovskite solar cells (PSCs). Herein, the strategy of amine (CH3NH2, MA) gas treatment is successfully exploited to synthesize high-quality MAI precursors and MAPbI3 perovskites. During MA gas treatment, ethylammonium (EA) cations in EAI are completely substituted with the MA cations from MA gas to generate pure MAI. Furthermore, cation substitution induced by MA gas treatment is further extended to convert 1D EAPbI3 perovskites to 3D MAPbI3 perovskites. Compared with traditional perovskites, 1D-to-3D perovskites show a much smoother surface and lower defect density. Consequently, the performance and stability of carbon-based PSCs without hole transport materials are considerably enhanced. Therefore, amine gas treatment has been proved to be a versatile and promising strategy for preparing high-quality perovskites and their precursors.

CsPbBr3 with a large band gap (∼2.3 eV) is a promising material for fabricating perovskite solar cells (PSCs) with a high open-circuit voltage (Voc) and high stability. However, a suitable method is still lacking for depositing high-quality CsPbBr3 films. Herein, we develop a novel strategy to deposit high-quality CsPbBr3 films by employing a porous CsPb2Br5 film as an intermediate layer. Highly porous CsPb2Br5 films composed of lamellar crystals were obtained by immersing Pb–Br precursor layers in a low-concentration CsBr IPA solution. The low CsBr concentration helped to widen the processing window of CsPb2Br5, while the low-polarity IPA solvent served to keep the film structure stable during the reaction. High-quality CsPbBr3 films with full coverage, high purity and low defect density were obtained by further converting the CsPb2Br5 films in a high-concentration CsBr solution. After introducing the optimized CsPbBr3 film into a carbon-based PSC without a hole transporting material (C-PSC), a power conversion efficiency (PCE) of 6.1% and a Voc of 1.38 V were achieved. Moreover, the devices without encapsulation show almost no PCE decay after 200 days of storage in ambient air (25–85% relative humidity, 20–30 °C) and at 80 °C (10–20% relative humidity) for over 1080 h.

Ocean wave is one of the promising renewable energy sources all around the world. In this paper, an electromagnetic ocean wave energy harvester (OWEH) based on efficient swing body mechanism is presented. A swing body senses the ultra-low frequency wave motion and drive the rotor of an electromagnetic power module (EPM) rotating at high speed through transmission gears. A series of electromagnetic and dynamic simulations were carried out to optimize the power generation capability of the OWEH. Additionally, the power management circuit is specially designed such that the generated power is able to charge a lithium battery and discharge an external load automatically. The OWEH is installed inside an ocean buoy and tested in the Yellow China Sea. When the peak wave height is greater than 0.6 m, the maximum peak-to-peak output voltage is 15.9 V. The corresponding output power is as high as 0.13 W and the maximum power density is 0.21 mW/cm3, where the internal resistance of the OWEH is 122 Ω. Due to the high performance and adaptability, the OWEH can potentially power many low power components, which opens a promising way for improving the life of ocean buoys. Considering the small dimension of 10 × 10 × 6.3 cm3, this OWEH can be mounted inside most buoys easily and realize the self-powered ocean buoys in the near future.

Thin protective films have been widely used for metal anticorrosion application. However, previous films either negatively influence the photoelectric property of metal surfaces or exhibit poor corrosion resistance. In this paper, an ultrathin adsorption film is built up through the effective use of linear/stereoscopic organosilicon. This kind of film is formed by the good 3-D shielding structure of a silicon resin and a linear oxosilane. Small molecule corrosion inhibitors fill the interstitial sites, leading to a compact composite structure. This film has little effect on the photoelectric property of the metal surface. Copper covered with this film achieves a contact angle of 118°and a protective efficiency of 99.34%, both of which are much higher than the previously reported for protective thin films. Moreover, such films could be adapted for various metal materials.

Carbon-based perovskite solar cells (PSCs) without hole transport material have attracted much attention due to their high stability. However, their power conversion efficiency (PCE) is still low because of the lack of suitable perovskite deposition methods. In this work, a facile solid-gas reaction method was explored to prepare high quality perovskite and the effects of precursor composition (PbI2, PbI2 + HI, HPbI3 and PbI2 + NH4I) on the CH3NH2 (MA) gas-induced perovskite were systematically investigated. The lack of H+/I− and/or HI suppressed the conversion of PbI2 precursor to MAPbI3, while rapid and complete conversion was achieved for (PbI2 + HI), HPbI3 and (PbI2 + NH4I) precursors. Compared with HPbI3 precursor, the presence of H2O molecules in (PbI2 + HI) precursor lowered the perovskite crystallinity, while the release of NH3 from (PbI2 + NH4I) precursor slower the interaction of MA molecules with MAPbI3 for achieving the highest quality MAPbI3 layer. The application of an anti-solvent treatment during precursor deposition further improved the quality of HPbI3 and (PbI2 + NH4I)-processed perovskite layers, which as a result, significantly promoted the photovoltaic performance of C-PSCs. Both devices exhibited considerably high stability, especially for the (PbI2 + NH4I)-processed C-PSCs, who did not show any PCE degradation after storage in air atmosphere at room temperature for 120 days.

We propose a glove based Human Machine Interface (HMI) designed for Virtual Reality (VR) and Augmented Reality (AR) applications. The proposed sensory glove uses facile designed triboelectric sensors to realize multi-dimensional motion recognition of gestures, and piezoelectric mechanical stimulators are also equipped for achieving the haptic feedback to user regarding the interactive events from virtual world. The developed HMI leverages machine learning technology to achieve real time object recognition, hence, we can manipulate virtual objects in VR/AR space by projecting sensory information from glove.

Triboelectric nanogenerators and sensors have been widely adopted for diversified energy harvesting and sensing applications, but the demonstrations of 3D information sensing and controlling are very limited. In this paper, we present a novel self-powered virtual reality 3D-control sensor (VR-3D-CS) based on triboelectric mechanism for controlling the attitude (both the position and rotation) of object in 3D virtual space. This innovative, cost-effective, simple-designed sensor has a symmetric 3D structure with eight separated sensing electrodes and two touching spheres as the interactive interface with human fingers for 3D force information sensing and VR controlling. Based on the coupling effect of triboelectrification and electrostatic induction, the VR-3D-CS generates different electric output signals in response to different operation manner that can be used to control the attitude of objects in 3D virtual space. The symmetrical 3D configuration design of the sensor enables the detection of 3D force from both the normal direction and shear direction. By employing vector properties of force and signal analysis from the eight sensing electrodes, detection of six-axis directions in 3D space is achieved by triboelectric mechanism for the first time. The VR-3D-CS has been demonstrated to be able to detect normal force in the range of 0–18 N. It can resolve the shear force direction with step resolution of at least 15°. Besides, due to the positive output voltage and low internal impedance, the VR-3D-CS is readily compatible with commercial portable signal processing system for signal analysis and controlling. Demonstration of the VR-3D-CS as interactive interface for Augmented Reality (AR) control is successfully realized. The robust structure, stable output performance and self-powered sensing property enable the device as an ideal human machine interface towards AR interface, batteryless and energy saving applications.

Flexible electronic devices are developing rapidly, especially in medical applications. This paper reports an arrayed flexible piezoelectric micromachined ultrasonic transducer (FPMUT) with a sandwich structure for adjuvant treatment of bone injury. To make the device conformable and stretchable for attaching to the skin surface, the flexible substrate of polydimethylsiloxane (PDMS) was combined with the flexible metal line interconnection between the bulk lead zirconate titanate (PZT) arrays. Simulations and experiments were carried out to verify the resonant frequency and tensile property of the reported FPMUT device. The device had a resonant frequency of 321.15 KHz and a maximum sound pressure level (SPL) of 180.19 dB at the distance of 5 cm in water. In addition, detailed experiments were carried out to test its acoustic performance with different pork tissues, and the results indicated good ultrasound penetration. These findings confirm that the FPMUT shows unique advantages for adjuvant treatment of bone injury.

Inorganic cesium lead halide perovskites with superb thermal stability show promise to fabricate long-term operational photovoltaic devices. However, the cubic phase (α) of CsPbI3 with an appropriate band gap is unstable in air. We discover that highly stable α-CsPbI3 can be obtained in dry air (temperature: 20–30 °C; humidity: 10–20%) by replacing PbI2 with HPbI3 in a one-step deposition solution. Furthermore, the band gap of HPbI3-processed α-CsPbI3 is advantageously reduced from 1.72 to 1.68 eV due to the existence of tensile lattice strain. By employing such an α-CsPbI3 film in carbon-based perovskite solar cells (C-PSCs), a power conversion efficiency (PCE) of 9.5% is achieved, which is a record value for the α-CsPbI3 PSCs without hole transport material. Most importantly, over 90% of the initial PCE is retained for nonencapsulated devices after 3000 h of storage in dry air. Therefore, HPbI3-based one-step deposition presents a promising strategy to prepare high-performance and air-stable α-CsPbI3 PSCs.

During the process of preparing coal tar pitch and petroleum asphalt, it is technically difficult to remove adhered asphalt through heating, chemical solvents, mechanical methods, etc. In this pape...

Gradient wetting surfaces are getting increasing attention due to their wide application in multiple fields such as droplet movement and biosorption. However, the fabrication processes of full gradient wetting surfaces are still complex and costly. In present work, a facile and low-cost chemical immersion method was used to create a full gradient wetting surface. By controlling the displacement time in Ni2+ solution, the prepared surfaces perform hydrophilic to superhydrophilic. After being modified by stearic acid, the gradient hydrophilic surfaces convert into hydrophobic. The surface morphology, composition, and wetting behaviors of the as-prepared surfaces were systematically studied and discussed. The gradient wetting property could be attributed to the change in microroughness and surface energy. In addition, these surfaces also exhibited excellent self-cleaning and wax prevention properties. Furthermore, high stability and corrosion resistance were also found for these surfaces, which further highlight their promising practical applications in many fields.

α-CsPbI3 with the most suitable band gap for all-inorganic perovskite solar cell (PSC) application faces an issue of phase instability at low temperature in an air atmosphere. Herein, through stoichiometric investigation, α-CsPbI3 is successfully obtained with excess CsI at 110 °C in an air atmosphere. By doping α-CsPbI3 with Sb, phase stability is further enhanced and the film morphology is also improved. Carbon-based perovskite solar cells (C-PSCs) based on CsPb0.96Sb0.04I3 achieve a promising power conversion efficiency (PCE) of 5.18%, a record value for α-CsPbI3-based PSCs without hole transport materials. Significantly, the CsPb0.96Sb0.04I3 C-PSCs retain 93% of the initial PCE after 37 days of storage in an air atmosphere. Therefore, the synergistic effect of non-stoichiometry and Sb-doping presents a promising strategy to design all-inorganic lead halide PSCs with high performance and stability.

Directly dispersing graphene in aqueous solutions, without chemical treatment or adding surfactants, remains an obstacle for plating metal-graphene composite coatings. In this study, graphene was prepared by electrochemical exfoliation of a graphite anode and directly dispersed in N, N-dimethylformamide (DMF)/H2O solutions containing CuSO4 (40, 80, and 120 g/L) without adding a surfactant. Cu/graphene composite coatings were electrodeposited in graphene dispersions. The Cu/graphene composite coating with the highest graphene content was obtained in a solution with 80 g/L CuSO4. The co-deposited graphene affected the preferred orientation and led to a different oxidation reaction rate between the Cu/graphene composite coatings. After thermal treatment, the Cu/graphene composite coating plated in the solution with 80 g/L CuSO4 exhibited the lowest oxidation degree. This indicates that co-deposited graphene reduces the oxidation degree of Cu/graphene composite coatings.

Alumina-silica particles contained zinc coatings on NdFeB are prepared by an in-situ electro-deposition method from alumina-silica sols contained plating bath. Alumina-silica sols with varied Si:Al ratio are prepared through the two step hydrolysis and condensation of aluminium isopropoxide (AIP) and tetraethyl orthosilicate(TEOS) with acid catalyst. As negative potential applied to NdFeB substrates promotes the deposition of zinc, it also causes the increase of hydroxyl ions concentration, which promotes the particle condensation and gel of alumina-silica sols. The effect of alumina-silica sols on the surface morphology, composition and performance of the electro deposited zinc coatings are studied for NdFeB substrate. The results show that the adsorption and gel of alumina-silica particles are along with the electro-deposition of zinc coating. As the Si:Al ratio increases in added sols, there are more alumina particles get embedded during electro-deposition, which affect the surface morphology and uniformity of zinc coating. Electrochemical and mechanical tests demonstrate that the embedded alumina-silica particles in zinc coatings may serve as inhibitors and help to improve the corrosion resistance and mechanical performance of the zinc coatings on NdFeB magnets.

Due to the extensive application of tin coatings, the electrodeposition mechanism, corrosion resistance and anti-discoloration performance have attracted attention in the past decades. In this paper, tin coatings containing sol particles were successfully prepared using the stable tin (IV) sols as the plating bath, based on the water-ethanol electrolytes. The particle size of the tin sols was largely in the range between 4 and 10 nm. When the sol contained 0.475 mol L − 1 SnCl 4 ·5H 2 O (Sol 2), the sol particles were uniformly deposited on tin coatings. The concentration of tin sol had a significant effect on the surface microstructure and preferred orientation of the electrodeposited tin coatings. The differences in nucleation process of the electrodeposition between tin sols and the aqueous acidic sulfate plating bath (sulfate bath) were revealed by electrochemical analysis. Compared with tin coatings deposited from sulfate bath, tin coatings deposited from Sol 2 had enhanced corrosion resistance and anti-discoloration performance.

Wireless sensor network (WSN) is an interestingly promising technology with many applications in intelligent environment-monitoring. Its energy consumption is, however, essentially challenged after it is deployed. In this paper, we developed a low-resonant-frequency piezoelectric energy harvesting device as an alternative to power WSN deployed in a weak vibration environment. An energy management module, equipped with a full-bridge rectifier (FBR), a fully self-powered voltage controller, and a logic-level protection circuit was designed to enable a regulated voltage to intermittently drive WSN for temperature monitoring. The power transfer efficiency of FBR reached 42%, presenting a good performance/cost ratio in the case of a relatively high open-circuit voltage of 8 V and a low rectified voltage of 3.3 V. The experimental results have demonstrated that the proposed WSN was successfully driven at an interval time of less than 1 min, and fully self-powered by the scavenged energy from the environmental vibration source of a 0.15-g acceleration and a 40-Hz vibration frequency.

Soft robots have significant advantages in terms of flexibility and adaptability, leading to potential applications in the bionics field. Inspired by the caterpillars in nature, this work proposed a soft caterpillar robot (SCR) by integrating two types of ultra-stretchable bionic sensors on a dual air-chamber pneumatic network structure. In order to realize self-powered tactile sensing, four triboelectric nanogenerator tactile sensors (TTSs) based on functional liquid metal (FLM) with thorny-structured bionic whiskers are developed and attached on the SCR. Meanwhile, two ultra-stretchable resistive strain sensors (RSSs) by using FLM are covered as the bionic skin to sense self-body deformation of the SCR. The TTS has a fast response time of 0.03 s and a minimum perception of 0.05 kPa, which can be very sensitive to the unknown stimulus of various materials. The RSS with a relatively high sensitivity of 2.94 and small hysteresis of 1.42% possess the ultra-stretchable ability of 180% strain, which helps to adapt and adjust its own body bending and crawling. The biological perception capabilities of the SCR play a crucial role in mimicking bionic actions and response in an unknown environment, such as escaping from unexpected attacks as well as adaptive crawling through an unknown tunnel environment.

The inorganic CsPbI3 perovskite obtained from dimethylammonium iodide (DMAI)-related strategies have greatly promoted the development of CsPbI3 perovskite solar cells (PSCs). However, deeper understandings are urgently needed to further enhance device performance. Herein, the crystallization processes of DMAI-based strategy are systematically studied and some new understandings are proposed. During annealing, β-phase-like CsPbI3 is first formed and then gradually transits to γ-phase-like structure. DMA ions tend more to form DMAPbI3 in the system, implying the amount of alloyed DMA ions in CsPbI3 would be very limited. In addition, the pre-generated Cs4PbI6 plays an important role in stabilizing CsPbI3 perovskite phase at low temperature. These findings help us to finely manipulate film composition, and the quality of CsPbI3 film is substantially improved after simultaneously suppressing the formation of δ-CsPbI3, minimizing DMAPbI3 residual and generating PbI2 passivator. More promisingly, the carbon-based CsPbI3 PSCs without hole transporter achieve a record efficiency of 14.6%.

Tremendous effort has been devoted to develop CeO2/polymer nanocomposites due to their excellent ultraviolet radiation absorption properties. However, there still exists many challenges in the successful incorporation of CeO2 nanoparticles into the polymer matrix because the ease aggregation of CeO2 nanoparticles. Here, we addressed the above issue by anchoring CeO2 nanoparticles on functionalized SiO2 spheres before their introduction into polymeric matrix, in which monodispersed vinyl group coated SiO2 spheres were synthesized by co-condensing tetraethoxysilane and 3-methacryloxypropyltrimethoxysilane, followed by coating with small size CeO2 nanoparticles (CeO2@M-SiO2) through chemical precipitation. The polymer composite film prepared by importing CeO2@M-SiO2 into fluorinated polyacrylate through miniemulsion polymerization exhibited enhanced UV absorption capacity, accompanied with an obvious improvement in hydrophobicity due to the increase in the surface roughness and fluorine content. Furthermore, the formation mechanism of the nanocomposite film was proposed: a polymer layer would form around the nanoparticles after film formation. This fluorinated polyacrylate/CeO2@M-SiO2 composite film is anticipated to be practically applied as outdoor coatings.

Energy harvesting technique has been identified as an innovative and environment-friendly way for powering micro sensors and electronic devices. In this paper, a hybrid generator based on triboelectric and electromagnetic mechanisms (TMHG), which provides two electrical power outputs at the same time, was proposed. The output performance in time and frequency domains are investigated at different initial gap distances and excitation accelerations. At an acceleration of 1 g and an initial gap distance of 5 mm, the maximum power outputs of electromagnetic and triboelectric parts can be obtained as 0.28 mW and 1.09 mW, respectively. The resonant frequency of the TMHG is as low as 23.5 Hz, making it more suitable to harvest energy from low frequency vibrations of less than 30 Hz. Besides, the operating bandwidth of TMHG can be adjusted by changing the initial gap distance according to the application requirements.

Iron sulfide has been proved to be a promising material for counter electrode (CE) of QDSCs in our previous work. However, the fill factor is still much below expectation, owing to the poor catalytic activity. Herein, iron sulfide nanosheets are embedded into porous carbon. This structure exhibits good interfacial contact between iron sulfide and carbon. As a result, it improves the stability of the CE, promotes the interfacial electron transfer rate between iron sulfide and carbon, and increases active sites leading to superior catalytic activity. Consequently, the QDSC based on this optimal structure obtains a power conversion efficiency of 5.61% with higher FF (0.64) compared with those with Pt or other conventional sulfide based CEs. Besides, we developed a novel facile, reproducible and printable preparation process: compositing and chemical conversion (3C).

Photopolymer film has been widely used in optical devices. However, the low initiator efficiency limits its wider development. In this study, Methylene blue (MB)/N-methyldiethanolamine (MDEA) and MB/1,4-diazabicyclo [2.2.2]octane (DABCO) were first adopted as initiator system in photopolymer film and compared their initiator system efficiencies with the common initiator system MB/triethanolamine (TEA) by a self-established single-beam exposure setup. The MB/MDEA showed the highest performance, while the MB/DABCO was the poorest. The quantum yield, bleaching rate and saturated exposure of the MB/MDEA were 3.31 times, 2.62 times and 2.49 times, respectively, higher than those of the MB/TEA. This order of initiator system efficiencies (MB/MDEA > MB/TEA > MB/DABCO) is exactly consistent with the order of proton transfer efficiencies of the electron donors (MDEA > TEA > DABCO). Furthermore, high proton transfer efficiency and excellent migration of electron donors are helpful to improve initiator system efficiency via surface micromorphology analysis. Keywords: Photopolymer films, Initiator system efficiency, Electron donor

Alumina film is effective for improving the corrosion resistance and protecting the magnetic properties of NdFeB magnets, but the complicated preparation method limits its application. In this study, we prepare alumina sol (AS) film on NdFeB magnets with an electric chemistry method from modified alumina sol. And a hydrothermal treatment (HTT) improves the combination and protection ability of AS film on NdFeB. Microstructural investigation suggests that the uniform AS film can be prepared on NdFeB under optimized electric conditions and the hydrothermal treatment helps to repair defects on the AS film. With the formation of electro-deposited AS film, the corrosion current density value reduces more than an order of magnitude and the intergranular corrosion of NdFeB is obviously suppressed in corrosive environments. The thermal stability of NdFeB magnets is also improved by the AS film. The morphology, composition and phase transition of the AS film are systematically investigated. In addition, the underlying formation mechanisms for electro-deposited AS film have been analyzed by zeta potential measurement and cathode polarization measurement at the sol–metal interface. These results have important implications for the preparation of protection film to prevent magnetic loss on sintered NdFeB magnets.

Superhydrophobic coatings have attracted significant attention due to their wide potential applications. However, the practical applications of the present artificial superhydrophobic coatings are not only hindered by their environmentally hazardous components, containing fluorinated materials and pungent organic solvents, but also by their poor material stabilities. Herein, a robust water-repellent organic–inorganic composite coating based on an aqueous dispersion was developed using a non-fluorinated material system consisting of a waterborne silicone–acrylic copolymer (SAC) and silica sol. Uniquely, the as-prepared SAC containing acid functional groups was first ionized in an alkaline environment, followed by introduction of the silica precursor into the SAC to generate the silica sol in situ. The abovementioned non-fluorinated material system favors the application of the simple spray technique for the superhydrophobic coating (157.7°) deposition, which can be flexibly employed on various substrates. The resulting composite coating, in which strong micro- and nano-scale roughness structures are embedded in the layer matrix, can withstand at least 200 abrasion cycles while retaining its superhydrophobicity. Moreover, the composite coating also shows significantly high resistance to acid/base, organic solvent, UV photodegradation (UVA light illumination for 96 h) and high-temperature heating (400 °C for 80 h). Furthermore, this environmentally friendly coating can be easily applied in the self-cleaning (in either air or oil environments) and oil/water separation fields.

Superhydrophobic coatings have drawn much attention in recent years for their wide potential applications. However, a simple, cost-effective, and environmentally friendly approach is still lacked. Herein, a promising approach using nonhazardous chemicals was proposed, in which multiple hydrophobic functionalized silica nanoparticles (SiO2 NPs) were first prepared as core component, through the efficient reaction between amino group containing SiO2 NPs and the isocyanate containing hydrophobic surface modifiers synthesized by normal alcohols, followed by simply spraying onto various substrates for superhydrophobic functionalization. Furthermore, to further improve the mechanical durability, an organic–inorganic composite superhydrophobic coating was fabricated by incorporating cross-linking agent (polyisocyanate) into the mixture of hydrophobic-functionalized SiO2 NPs and hydroxyl acrylic resin. The hybrid coating with cross-linked network structures is very stable with excellent mechanical durability, sel...

The device instability has been an important issue for hybrid organic–inorganic halide perovskite solar cells (PSCs). This work intends to address this issue by exploiting inorganic perovskite (CsPbBr3) as light absorber, accompanied by replacing organic hole transport materials (HTM) and the metal electrode with a carbon electrode. All the fabrication processes (including those for CsPbBr3 and the carbon electrode) in the PSCs are conducted in ambient atmosphere. Through a systematical optimization on the fabrication processes of CsPbBr3 film, carbon-based PSCs (C-PSCs) obtained the highest power conversion efficiency (PCE) of about 5.0%, a relatively high value for inorganic perovskite-based PSCs. More importantly, after storage for 250 h at 80 °C, only 11.7% loss in PCE is observed for CsPbBr3 C-PSCs, significantly lower than that for popular CH3NH3PbI3 C-PSCs (59.0%) and other reported PSCs, which indicated a promising thermal stability of CsPbBr3 C-PSCs.

Carbon-based hole transport material (HTM)-free perovskite solar cells (PSCs) have attracted intense attention due to their relatively high stability. However, their power conversion efficiency (PCE) is still low, especially for the simplest paintable carbon-based PSCs (C-PSCs), whose performance is greatly limited by poor contact at the perovskite/carbon interface. To enhance interface contact, it is important to fabricate an even-surface perovskite layer in a porous scaffold, which is not usually feasible due to roughness of the crystal precursor. Herein, colloidal engineering is applied to replace the traditional crystal precursor with a colloidal precursor, in which a small amount of dimethyl sulfoxide (DMSO) is added into the conventional PbI2 dimethylformamide (DMF) solution. After deposition, PbI2(DMSO) adduct colloids (which are approximately tens of nanometers in size) are stabilized and dispersed in DMF to form a colloidal film. Compared with PbI2 and PbI2(DMSO) adduct crystal precursors deposit...

Throat cancer treatment involves surgical removal of the tumor, leaving patients with facial disfigurement as well as temporary or permanent loss of voice. Surface electromyography (sEMG) generated from the jaw contains lots of voice information. However, it is difficult to record because of not only the weakness of the signals but also the steep skin curvature. This paper demonstrates the design of an imperceptible, flexible epidermal sEMG tattoo-like patch with the thickness of less than 10 μm and peeling strength of larger than 1 N cm−1 that exhibits large adhesiveness to complex biological surfaces and is thus capable of sEMG recording for silent speech recognition. When a tester speaks silently, the patch shows excellent performance in recording the sEMG signals from three muscle channels and recognizing those frequently used instructions with high accuracy by using the wavelet decomposition and pattern recognization. The average accuracy of action instructions can reach up to 89.04%, and the average accuracy of emotion instructions is as high as 92.33%. To demonstrate the functionality of tattoo-like patches as a new human–machine interface (HMI) for patients with loss of voice, the intelligent silent speech recognition, voice synthesis, and virtual interaction have been implemented, which are of great importance in helping these patients communicate with people and make life more enjoyable. Tattoo-like wearable electronic patches could help patients who have lost the capacity for speech to communicate once again. The aftermath of surgeries for mouth and throat cancers can result in permanent voice loss, but the information needed to decode speech can still be recovered from the movements of facial muscles. Researchers led by Hongmiao Zhang and Lining Sun at China’s Soochow University and Chengkuo Lee at the National University of Singapore have developed flexible sensors that can be applied to the skin to capture this information. In a series of tests with human volunteers, they demonstrated that vocalization-associated muscle activity collected from these patches could be computationally decoded with up to 92% accuracy. Similar devices could eventually be coupled to voice synthesizers or other devices to help restore normal speech after cancer surgery.

This paper proposes an impact-based micro piezoelectric energy harvesting system (PEHS) working with the frequency up-conversion mechanism. The PEHS consists of a high-frequency straight piezoelectric cantilever (SPC), a low-frequency S-shaped stainless-steel cantilever (SSC), and supporting frames. During the vibration, the frequency up-conversion behavior is realized through the impact between the bottom low-frequency cantilever and the top high-frequency cantilever. The SPC used in the system is fabricated using a new micro electromechanical system (MEMS) fabrication process for a piezoelectric thick film on silicon substrate. The output performances of the single SPC and the PEHS under different excitation accelerations are tested. In the experiment, the normalized power density of the PEHS is 0.216 &mu, W&middot, g&minus, 1&middot, Hz&minus, cm&minus, 3 at 0.3 g acceleration, which is 34 times higher than that of the SPC at the same acceleration level of 0.3 g. The PEHS can improve the output power under the low frequency and low acceleration scenario.

In this paper, an impact-based frequency up-converted piezoelectric energy harvesting system (PEHS) is proposed and fabricated using MEMS piezoelectric thick film technology. The PEHS mainly consists of a high-frequency piezoelectric cantilever (PC-H) with resonate frequency of 935 Hz and a low-frequency stainless-steel cantilever (SC-L) with resonate frequency of 23 Hz. Under the external low-frequency vibration excitation, the SC-L at the bottom impacts the PC-H during the movement, in this way the low-frequency external vibration is converted to high-frequency piezoelectric cantilever vibration. When the PC-H is triggered to vibrate at 935 Hz, the maximum voltage output is 74 mV at 1.0 g. Then incorporate the PC-H with SC-L and form the PEHS, at driving frequency of 20 Hz to 34 Hz, the maximum voltage output and 3dB bandwidth of the PEHS reach 1220 mV and 4.7 Hz, respectively. The maximum voltage output of the PEHS (1220 mV) is more than 16 times of that of the single PC-H (74 mV).

This paper reports an energy harvester based on pendulum to harvest energy from ultra-low frequency ocean waves. When the eccentric mass pendulum is subjected to an excitation wave, it generates a large angle of oscillation or even rotation. The kinetic energy collected by the device is transmitted to an electromagnetic power generation module through the gears. The motion behavior of the device under different wave amplitudes and frequencies are explored by using ADAMS software. The shape, size and material of the mass pendulum are optimized. In the simulation, the maximum open-circuit voltage of the device can reach to 15 V under the wave amplitude of 20 cm and frequency of 1 Hz. It has the maximum output power of 0.4 W with an external resistance of 100 Ω. When tested in a large experimental tank, the output of the device is also good. The maximum open-circuit voltage and power of the device can reach to 8 V and 0.16 W under the wave amplitude of 20 cm and period of 3 s. The volume of the device is 100 * 100 * 56 mm3.

Surface electromyography (sEMG) signals generated by the muscles of the lower jaw contain corresponding voice information when talking. However, it's very hard to collect sEMG signals from the jaw because of not only the weakness of the signals but also the sharp skin curvature of this area. This paper reports a super-flexible and high-sensitive epidermal sEMG electrode patch to measure sEMG signals of the jaw from which the voice information can be extracted for speech recognition. This epidermal sEMG patch can be effectively attached to the jaw and the interconnection wire in the form of double wave can stretch more than 100%. From the characteristic of envelopes of the signals, it shows good consistency when the tester speak the same word and obvious difference can be detected when the tester speak different words. Four-layer wavelet decomposition is used to reduce noise in sMEG records and the eigenvectors are extracted from wavelet coefficients to characterize each trial. The experimental result shows that the average accuracy of the three pronunciations is about 71.7%. The accuracy of “hello” reaches up to 91%. In the future his epidermal sEMG electrode patch has great potential for the application of silent speech recognition.

Residual stress can dramatically hamper the performance of piezoelectric micromachined ultrasound transducers (pMUTs), in particular the transmitting sensitivity. This paper reports a series of square pMUTs with enhanced transmitting sensitivity through V-shaped springs in different angles. The V-shaped springs can release the residual stress through self-deformation, which contributes to a flat vibrating membrane rather than a curved one. A flat vibrating membrane conduces to a large vibration amplitude. Consequently, the transmitting sensitivity of the pMUT with 150° V-shaped springs is measured as 50.9 nm/V, which is 203% higher than that of the pMUT without springs. The enhanced pMUTs have advantages in various applications of emission ultrasound.

In recent years, microencapsulation technology has drawn much attention due to its wide applications. Added to the coating as a dry powder, the microcapsules contain a liquid that can repair the film if released into the cracks. However, there is still a lack of synthesis strategies for microcapsules with excellent strength, solvent resistance and thermal stability. Herein, organic–inorganic hybrid nano/microcapsules loaded with isophorone diisocyanate (IPDI) were prepared via interfacial polymerization in Pickering emulsion. The diameter of the resultant capsules ranged from 468 nm to 1106 nm, and the thick shells were densely packed with silica nanoparticles. To evaluate the resistance properties of the nano/microcapsules, thermogravimetric analysis (TGA) tests showed that the capsules have a high initial evaporation temperature at about 340 °C; titration tests indicated that the capsules exhibited outstanding resistance to xylene and acetone. For capsules characterized by AFM, the compressive modulus could reach up to 16–19 GPa, which proved their excellent mechanical property. The morphology of the nanocapsules in different preparation periods was also studied, and it was found that the shell wall was closely packed with silica nanoparticles. The structure of the shell wall and the chemical reaction between organic and inorganic materials improved the hardness of the nano/microcapsules. Furthermore, the resultant capsules exhibited self-healing ability in an organic silicon resin coating.

Al2O3-contained zinc coatings with enhanced protective and mechanical performances were prepared on NdFeB magnets by in situ electro-deposition methods from the zinc plating baths containing alumina sol. The positively charged alumina sol particles migrate to the NdFeB cathode and then gel along with zinc on the cathode surface, which changes the electro-deposition process of zinc. As a result, the surface morphology and phase structure of the zinc coating is significantly changed. The incorporation of alumina particles achieves a denser zinc coating with a smaller grain size and the hardness is well improved. By increasing alumina sol concentration in the plating bath, the micro-hardness and wear resistance of the zinc coatings gradually increased. What's more, the alumina sol addition also improved the corrosion resistance of zinc coatings. When 20 wt. % alumina sol is added, the corrosion potential of the zinc coating is positively shifted for 168 mV and the corrosion current was more than one order magnitude lower than the blank one. Therefore, this approach shows great promise to obtain alumina-contained zinc coatings with enhanced anti-corrosion properties and mechanical properties.

The past few years have witnessed the rapid innovation of wearable chemical sensors that induce impacts on various areas of our daily life. As the emerging Internet of Thing (IoT), wearable chemical sensors hold considerable promise not only for healthcare and fitness applications but also for other diversified applications ranging from environment monitoring to security/forensic identification. With the vision of more versatile, convenient, communicating and integrated, this review provides a comprehensive overview of the recent progress of wearable chemical sensors and systems. First, in terms of healthcare application, the development of wearable chemical sensors for markers detection from sweat is reviewed in the aspect of transduction mechanism and structural configuration (i.e., soft/soft-hard integration patch, tattoo, and microfluidics). Then the evolution of wearable tear and saliva sensors from simple sensor design to integrated system (e.g., communication module and power supply integration) are reviewed. Next, treatment (i.e., drug delivery), as an indispensable part of close loop sensing-therapeutic system establishment, is reviewed via the representatives of microneedle technology. Additionally, the progress of wearable chemical sensors for environmental monitoring and security/forensic applications are presented, showing the development of self-sustainable/on-site testing systems. With this review, we believe the development trend of wearable chemical sensors is towards multifunctional, sensing-therapeutic, self-powered and integrated systems.

The power conversion efficiencies of organic-inorganic hybrid perovskite solar cells (PSCs) have been boosted from 3.8% to over 25% in about ten years. However, low device stability still impedes their practical applications. In the last few years, the inorganic PSCs based on carbon electrodes (C–PSCs) have gradually become one of the promising resolutions, and up to now, much progress has been made. Herein, recent developments in C–PSCs, including (1) device structure and working principles, (2) categorical progress of CsPbBr3, CsPbI3-xBrx, CsPbI3 and other inorganic C–PSCs, are reviewed. Promising research directions (e.g. developing suitable deposition methods, improving phase stability, tuning energy band structure, modifying perovskite/carbon interface and exploiting new inorganic perovskites) are then suggested to promote the development of inorganic C–PSCs.

Wax deposition is a detrimental problem that happens during the crude oil production and transportation. To inhibit wax deposition, a conversion coating with excellent antiwax property is developed using a quite simple and environmentally friendly method. The surface morphology, composition and wetting behaviors were characterized by SEM, EDS, FTIR and contact angle meter. A possible mechanism of antiwax is proposed, which can be calculated from water film theory. Due to the simple fabrication and excellent performance, this conversion coating is expected to widely apply in petroleum industry.

Binary nanoscale interfacial materials are fundamental issues in many applications for smart surfaces. A binary nanoscale interface with binary surface morphology and binary wetting behaviors has been prepared by a facile wet-chemical method. The prepared surface presents superhydrophobicity and high adhesion with the droplet at the same time. The composition, surface morphology, and wetting behaviors of the prepared surface have been systematic studied. The special wetting behaviors can be contributed to the binary nanoscale effect. The stability of the prepared surface was also investigated. As a primary application, a facile device based on the prepared binary nanoscale interface with superhydrophobicity and high adhesion was constructed for microdroplet transportation.

Hydrophilic anti-fogging coatings are necessary for transparent substrates, which can enable water to spread uniformly to avoid fogging. However, the transparency and the adherence to the underlying substrate of the anti-fogging coating reported are not yet optimal. In this article, we reported on a hydrophilic anti-fogging coating that could maintain good transparency and adherence. The coating was prepared by a waterborne polyacrylate modified silica sol precursor. Firstly, a silica sol precursor was synthetized by hydrolyzing tetraethoxysilane in an aqueous medium and then was introduced into the polyacrylate emulsion to in situ generate the crosslinking structure. The presence of the silica sol improved the hydrophilicity of the waterborne polyacrylate emulsion coating with a water contact angle as low as 11° (static water contact angle). And water droplets could spread out rapidly, which afforded the polyacrylate/silica composite coating with good anti-fogging ability (without forming water droplets) in a humidifier test. Furthermore, transmittance and adherence of the substrate were well maintained after the deposition of the composite coating.

Alumina film on NdFeB magnets is effective for improving the corrosion resistance and protecting the magnetic properties of the magnets, but the complicated preparation method limits its application. In this study, we prepare alumina-containing conversion film on NdFeB magnets using the reaction of NdFeB magnets with modified alumina sol at the interface. With the successful deposition of the alumina sol-containing conversion film (AS film), the corrosion current density value reduces by more than an order of magnitude and the intergranular corrosion is obviously suppressed in corrosive environment. The thermal stability and magnetic properties of NdFeB magnets are also improved by the AS film. The morphology, composition and structural optimization of the film are systematically investigated. Microstructural investigation suggests that the AS film is uniform and helps to repair defects on the NdFeB surface. Structure analyses reveal that the film is amorphous and protects the magnetic performance. In addition, the underlying mechanism for the formation of the AS film has been analyzed by zeta potential measurement and the potential of zero charge (Epzc) measurement at the sol–metal interface. These results have important implications for the preparation of no-magnetic-loss protection films on sintered NdFeB magnets.

Superhydrophilicity and underwater superoleophobicity are fundamental issues in many applications for special wettable surfaces. In this work, special wetting behaviors were achieved by using an ecologically friendly wet chemical method. The prepared coatings with porous structure present superhydrophilicity and underwater superoleophobicity. The effects of the reaction conditions, such as pH values and conversion duration, on the morphology and wetting behaviors of the prepared coatings were also studied. A wax deposition test based on the cold-finger method was carried out and good performance was displayed. A possible wax prevention mechanism is proposed, which can be calculated from water film theory. The corrosion resistance and stability of the prepared coatings were also measured. The prepared coatings with special wetting behaviors offer significant insight into the design of anti-wax materials in crude oil transition.

Alumina sol was prepared with ascorbic acid (also known as Vitamin C, Vc) as peptizer instead of the traditional used HCl. The prepared sol was then used for the anti-corrosion protection of NdFeB magnets. After substitution, the protective ability of the alumina sol film on NdFeB magnets improved significantly. Systematic comparison of the two alumina sol film were taken. Result showed that the Vc peptized alumina sol (AS-Vc) film showed a more uniform and complete surface which can help repair the defects on NdFeB surface without causing other damages. The electrochemical test showed the corrosion current density of NdFeB with AS-Vc film further reduced to 7.682 × 10−8 A cm-2, which is almost one-third of that in AS-Cl film. Along with the salt-water immersion test result, the data showed the corrosion is obviously suppressed after substitution. What’s more, the differences of the film formation mechanism between the two alumina films were investigated. By comparison, NdFeB in AS-Vc showed an about 200 mV more positive open circuit potential than it in HCl peptized alumina sol (AS-Cl), which means less redox reaction during the film formation process. Above all, the Vc peptized alumina sol provides higher corrosion resistance ability for NdFeB, which is wery suitable for the simple protection of NdFeB materials.